1. Field of the Invention
This invention relates to synthetic absorbable sutures, and more particularly, to sutures prepared from a novel polymer derived from lactide and glycolide.
2. Description of the Prior Art
Homopolymers and copolymers of lactide and glycolide are well-known in the preparation of synthetic absorbable sutures as disclosed, for example, in U.S. Pat. Nos. 3,636,956, 2,703,316, 3,468,853, and 3,565,869. Preferred polymers are polyglycolide or copolymers of glycolide with L(-)-lactide which are highly crystalline, fiber-forming materials that can be extruded into fibers and have good physical properties and reasonable absorption times when implanted in living animal tissue.
Copolymers of lactide and glycolide for use in the preparation of surgical sutures are presently limited to a narrow range of compositions, namely, those copolymers which contain about 80 percent by weight glycolide. Random copolymers containing less than about 80 percent glycolide to about 40 percent glycolide are found to be of low crystallinity, and sutures prepared from such polymers are characterized by low tensile strength and poor strength retention in living animal tissue. Polymers containing less than about 40 percent by weight glycolide and up to 100 percent lactide are fiber-forming and result in strong suture materials, but tensile strength retention and/or the rate of absorption of such sutures in living animal tissue is typically less than desired.
It is an object of the present invention to provide copolymers of lactide and glycolide having less than about 75 percent by weight glycolide which are nevertheless highly crystalline, fiber-forming materials. It is another object of this invention to provide absorbable sutures comprised of a copolymer of lactide and glycolide containing less than about 75 percent glycolide. It is a further object of this invention to provide a method for preparing highly crystalline polymers of lactide and glycolide containing from about 50 percent to 75 percent by weight glycolide.